Resource configuration and reservation for sidelink communications

ABSTRACT

Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for efficiently selecting resources for sidelink communications in a shared spectrum while allowing other user equipment (UEs) a chance to gain access to the shared spectrum. In one aspect, a UE may transmit sidelink data to another UE in accordance with a frequency hopping pattern to randomize interference and improve throughput. According to some aspects, the first UE may transmit the sidelink data on a first set of interleaved frequency resources in a first time interval and a second, different set of interleaved frequency resources in a second time interval. In another aspect, a UE may rely on feedback from other UEs to determine when reserved resources are released, and the UE may use the released resources for sidelink communications.

CROSS REFERENCE

The present application for patent claims the benefit of U.S.Provisional Patent Application No. 62/929,661 by FAKOORIAN et al.,entitled “RESOURCE CONFIGURATION AND RESERVATION FOR SIDELINKCOMMUNICATIONS,” filed Nov. 1, 2019, assigned to the assignee hereof,and expressly incorporated by reference herein.

BACKGROUND

The following relates generally to wireless communications and morespecifically to resource configuration and reservation for sidelinkcommunications.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong-Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform spread orthogonal frequency division multiplexing(DFT-S-OFDM).

A wireless multiple-access communications system may include a number ofbase stations or network access nodes, each simultaneously supportingcommunication for multiple communication devices, which may be otherwiseknown as user equipment (UEs). Some wireless communications systems maysupport sidelink communications between UEs over a shared radiofrequency spectrum. In such systems, a UE may contend for access to theshared radio frequency spectrum to transmit sidelink data to another UE,and it may be challenging for the UE to gain access to the shared radiofrequency spectrum. Improved techniques for facilitating sidelinkcommunications over a shared radio frequency spectrum may be desirable.

SUMMARY

The present disclosure relates to methods, systems, devices, andapparatuses that support resource configuration and reservation forsidelink communications. Generally, the described techniques provide forefficiently selecting resources for sidelink communications in a sharedspectrum while allowing other UEs a chance to gain access to the sharedspectrum. In one aspect, a UE may transmit sidelink data to another UEin accordance with a frequency hopping pattern to randomize interferenceand improve throughput. For instance, the UE may transmit the sidelinkdata on a first set of interleaved frequency resources in a first timeinterval and a second, different set of interleaved frequency resourcesin a second time interval. In another aspect, a UE may rely on hybridautomatic repeat request (HARQ) feedback from other UEs to determinewhen reserved resources are released, and the UE may use the releasedresources for sidelink communications. For instance, when a first UEreceives HARQ feedback indicating that a transmission from a second UEwas successfully received by a third UE, the first UE may use resourcesreserved by the second UE (e.g., for a subsequent retransmission) totransmit sidelink data to a fourth UE.

A method of wireless communication implemented by a first UE isdescribed. The method may include identifying a resource poolconfiguration indicating resources in a shared radio frequency spectrumband available to the first UE for sidelink communications, theresources comprising a plurality of contiguous time intervals,identifying a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting sidelink data in afirst time interval of the set of contiguous time intervals and a secondset of interleaved frequency resources for transmitting the sidelinkdata in a second time interval of the set of contiguous time intervals,and transmitting, to a second UE, the sidelink data on the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern.

An apparatus for wireless communication at a first UE is described. Theapparatus may include a processor, memory coupled with the processor,and instructions stored in the memory. The instructions may beexecutable by the processor to cause the apparatus to identify aresource pool configuration indicating resources in a shared radiofrequency spectrum band available to the first UE for sidelinkcommunications, the resources comprising a plurality of contiguous timeintervals, identify a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting sidelink data in afirst time interval of the set of contiguous time intervals and a secondset of interleaved frequency resources for transmitting the sidelinkdata in a second time interval of the set of contiguous time intervals,and transmit, to a second UE, the sidelink data on the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern.

Another apparatus for wireless communication at a first UE is described.The apparatus may include means for identifying a resource poolconfiguration indicating resources in a shared radio frequency spectrumband available to the first UE for sidelink communications, theresources comprising a plurality of contiguous time intervals,identifying a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting sidelink data in afirst time interval of the set of contiguous time intervals and a secondset of interleaved frequency resources for transmitting the sidelinkdata in a second time interval of the set of contiguous time intervals,and transmitting, to a second UE, the sidelink data on the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern.

A non-transitory computer-readable medium storing code for wirelesscommunication at a first UE is described. The code may includeinstructions executable by a processor to identify a resource poolconfiguration indicating resources in a shared radio frequency spectrumband available to the first UE for sidelink communications, theresources comprising a plurality of contiguous time intervals, identifya frequency hopping pattern including a first set of interleavedfrequency resources for transmitting sidelink data in a first timeinterval of the set of contiguous time intervals and a second set ofinterleaved frequency resources for transmitting the sidelink data in asecond time interval of the set of contiguous time intervals, andtransmit, to a second UE, the sidelink data on the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for performing alisten-before-talk procedure to gain access to the shared radiofrequency spectrum band for a channel occupancy time to transmit thesidelink data to the second UE, the channel occupancy time spanning atleast the first time interval and the second time interval of theplurality of contiguous time intervals. Some aspects of the method,apparatuses, and non-transitory computer-readable medium describedherein may further include operations, features, means, or instructionsfor receiving control information indicating at least one set ofinterleaved frequency resources that is available for each time intervalof the plurality of contiguous time intervals, wherein identifying thefrequency hopping pattern comprising the first set of interleavedfrequency resources in the first time interval and the second set ofinterleaved frequency resources in the second time interval is based atleast in part on receiving the control information.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting, in thefirst time interval, an indication of the first set of interleavedfrequency resources used for transmitting the sidelink data in the firsttime interval, and transmitting, in the second time interval, anindication of the second set of interleaved frequency resources used fortransmitting the sidelink data in the second time interval. Some aspectsof the method, apparatuses, and non-transitory computer-readable mediumdescribed herein may further include operations, features, means, orinstructions for transmitting, in the first time interval, an indicationof the second set of interleaved frequency resources used fortransmitting the sidelink data in the second time interval. Some aspectsof the method, apparatuses, and non-transitory computer-readable mediumdescribed herein may further include operations, features, means, orinstructions for transmitting, in the first time interval, the secondtime interval, or both, an indication of the frequency hopping patternused by the first UE to transmit sidelink data on the first set ofinterleaved frequency resources in the first time interval and on thesecond set of interleaved frequency resources in the second timeinterval.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting anindication of gaps in the first time interval, the second time interval,or both, allocated for other UEs to perform listen-before-talkprocedures to gain access to the shared radio frequency spectrum band.In some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein, respective sets ofinterleaved frequency resources available to the first UE for sidelinkcommunications in each time interval of the set of contiguous timeintervals may be based on a subcarrier spacing of the time interval, asidelink identification (ID) of the first UE, a resource pool ID of therespective set of interleaved frequency resources, one or moreparameters associated with group hopping of frequency resources, or acombination thereof.

A method of wireless communication implemented by a first UE isdescribed. The method may include identifying that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receiving a feedbackmessage transmitted by a third UE acknowledging receipt of atransmission of first sidelink data from the second UE, identifyingresources reserved for a retransmission of the first sidelink data fromthe second UE to the third UE, initiating a listen-before-talk procedureto gain access to the identified resources for at least one interval ofthe channel occupancy time, and transmitting, based on a result of thelisten-before-talk procedure, second sidelink data to a fourth UE on theidentified resources based on receiving the feedback message.

An apparatus for wireless communication at a first UE is described. Theapparatus may include a processor, memory coupled with the processor,and instructions stored in the memory. The instructions may beexecutable by the processor to cause the apparatus to identify that asecond UE has reserved a shared radio frequency spectrum band forsidelink communications in a channel occupancy time, the channeloccupancy time spanning a set of contiguous time intervals, receive afeedback message transmitted by a third UE acknowledging receipt of atransmission of first sidelink data from the second UE, identifyresources reserved for a retransmission of the first sidelink data fromthe second UE to the third UE, initiate a listen-before-talk procedureto gain access to the identified resources for at least one interval ofthe channel occupancy time, and transmit, based on a result of thelisten-before-talk procedure, second sidelink data to a fourth UE on theidentified resources based on receiving the feedback message.

Another apparatus for wireless communication at a first UE is described.The apparatus may include means for identifying that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receiving a feedbackmessage transmitted by a third UE acknowledging receipt of atransmission of first sidelink data from the second UE, identifyingresources reserved for a retransmission of the first sidelink data fromthe second UE to the third UE, initiating a listen-before-talk procedureto gain access to the identified resources for at least one interval ofthe channel occupancy time, and transmitting, based on a result of thelisten-before-talk procedure, second sidelink data to a fourth UE on theidentified resources based on receiving the feedback message.

A non-transitory computer-readable medium storing code for wirelesscommunication at a first UE is described. The code may includeinstructions executable by a processor to identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receive a feedback messagetransmitted by a third UE acknowledging receipt of a transmission offirst sidelink data from the second UE, identify resources reserved fora retransmission of the first sidelink data from the second UE to thethird UE, initiate a listen-before-talk procedure to gain access to theidentified resources for at least one interval of the channel occupancytime, and transmit, based on a result of the listen-before-talkprocedure, second sidelink data to a fourth UE on the identifiedresources based on receiving the feedback message.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving controlinformation indicating that the resources reserved for theretransmission may be released upon the third UE acknowledging receiptof the transmission of the first sidelink data. In some aspects of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the control information further indicates a quantityof slots after receiving the feedback message that the first UE may beto wait before transmitting the second sidelink data on the resourcesreserved for the retransmission. In some aspects of the method,apparatuses, and non-transitory computer-readable medium describedherein, the control information further indicates that the first UE maybe eligible to transmit using the identified resources for the at leastone interval of the channel occupancy time. In some aspects of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the control information includes sidelink controlinformation or downlink control information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates aspects of a wireless communications system thatsupports resource configuration and reservation for sidelinkcommunications in accordance with aspects of the present disclosure.

FIG. 2 illustrates aspects of non-contiguous time-domain resources usedfor sidelink communications in accordance with aspects of the presentdisclosure.

FIG. 3 illustrates aspects of a wireless communications system thatsupports resource configuration and reservation for sidelinkcommunications in accordance with aspects of the present disclosure.

FIG. 4 illustrates aspects of interleaved frequency resources used forsidelink communications in contiguous time-domain resources inaccordance with aspects of the present disclosure.

FIG. 5 illustrates aspects of a process flow that supports resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure.

FIG. 6 illustrates aspects of a process flow that supports resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure.

FIGS. 7 and 8 show block diagrams of devices that support resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure.

FIG. 9 shows a block diagram of a communications manager that supportsresource configuration and reservation for sidelink communications inaccordance with aspects of the present disclosure.

FIG. 10 shows a diagram of a system including a device that supportsresource configuration and reservation for sidelink communications inaccordance with aspects of the present disclosure.

FIGS. 11 through 13 show flowcharts illustrating methods that supportresource configuration and reservation for sidelink communications inaccordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless communications systems may support sidelink communicationsbetween user equipment (UEs) in a shared spectrum. In such systems, apool of resources (e.g., a time and frequency resource pool (TFRP)) maybe configured for sidelink communications in the shared spectrum, and aUE may perform a listen-before-talk (LBT) procedure to gain access tothe resources for a sidelink transmission to another UE. In some cases,a wide range of categories of sidelink communications may be supported(e.g., for internet of things (IoT) applications, vehicle-to-everything(V2X) communications, etc.), and the number of UEs attempting to gainaccess to the TFRP in the shared spectrum may be high. In such cases,techniques for improving the quality of sidelink transmissions may bedesirable to limit the number of times a UE has to acquire or reacquireaccess to the shared spectrum to transmit or retransmit sidelink data.In addition, techniques for releasing reserved, unused resources may bedesirable to allow more UEs to gain access to the shared spectrum.

As described herein, UEs in a wireless communications system may supporttechniques for efficiently selecting resources for sidelinkcommunications in a shared spectrum while allowing other UEs a chance togain access to the shared spectrum. In one aspect, a UE may transmitsidelink data to another UE in accordance with a frequency hoppingpattern to randomize interference and improve throughput. As a result,an original transmission from the UE may be likely to be receivedsuccessfully, and the UE may avoid reacquiring access to the sharedspectrum for a retransmission. In another aspect, a UE may rely onhybrid automatic repeat request (HARQ) feedback from other UEs todetermine when reserved resources are released, and the UE may use thereleased resources for sidelink communications. For instance, when afirst UE receives HARQ feedback indicating that a transmission from asecond UE was successfully received by a third UE, the first UE may useresources reserved by the second UE (e.g., for a subsequentretransmission) to transmit sidelink data to a fourth UE (e.g., thesecond UE may release the reserved, unused resources).

Aspects of the disclosure introduced above are described below in thecontext of a wireless communications system. Aspects of processes andsignaling exchanges that support resource configuration and reservationfor sidelink communications are then described. Aspects of thedisclosure are further illustrated by and described with reference toapparatus diagrams, system diagrams, and flowcharts that relate toresource configuration and reservation for sidelink communications.

FIG. 1 illustrates aspects of a wireless communications system 100 thatsupports resource configuration and reservation for sidelinkcommunications in accordance with aspects of the present disclosure. Thewireless communications system 100 includes base stations 105, UEs 115,and a core network 130. According to some aspects, the wirelesscommunications system 100 may be a Long-Term Evolution (LTE) network, anLTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR)network. In some cases, wireless communications system 100 may supportenhanced broadband communications, ultra-reliable (e.g., missioncritical) communications, low latency communications, or communicationswith low-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB orgiga-NodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105 (e.g., in a physical uplink control channel(PUCCH) or a physical uplink shared channel (PUSCH)), or downlinktransmissions from a base station 105 to a UE 115 (e.g., in a physicaldownlink control channel (PDCCH) or a physical downlink shared channel(PDSCH)). Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up a portion of the geographic coverage area 110,and each sector may be associated with a cell. According to someaspects, each base station 105 may provide communication coverage for amacro cell, a small cell, a hot spot, or other types of cells, orvarious combinations thereof. According to some aspects, a base station105 may be movable and therefore provide communication coverage for amoving geographic coverage area 110. According to some aspects,different geographic coverage areas 110 associated with differenttechnologies may overlap, and overlapping geographic coverage areas 110associated with different technologies may be supported by the same basestation 105 or by different base stations 105. The wirelesscommunications system 100 may include a heterogeneous LTE/LTE-A/LTE-APro or NR network in which different types of base stations 105 providecoverage for various geographic coverage areas 110.

The term “cell” may refer to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. According to someaspects, a carrier may support multiple cells, and different cells maybe configured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

The term “carrier” may refer to a set of radio frequency spectrumresources having a defined physical layer structure for supportingcommunications over a communication link 125. According to some aspects,a carrier of a communication link 125 may include a portion of a radiofrequency spectrum band that is operated according to physical layerchannels for a given radio access technology. Each physical layerchannel may carry user data, control information, or other signaling. Acarrier may be associated with a pre-defined frequency channel (e.g., anevolved universal mobile telecommunication system terrestrial radioaccess (E-UTRA) absolute radio frequency channel number (EARFCN)) andmay be positioned according to a channel raster for discovery by UEs115. Carriers may be downlink or uplink (e.g., in an FDD mode), or beconfigured to carry downlink and uplink communications (e.g., in a TDDmode). According to some aspects, signal waveforms transmitted over acarrier may be made up of multiple sub-carriers (e.g., usingmulti-carrier modulation (MCM) techniques such as orthogonal frequencydivision multiplexing (OFDM) or discrete Fourier transform spread OFDM(DFT-S-OFDM)).

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer.According to some aspects, a UE 115 may also refer to a wireless localloop (WLL) station, an Internet of Things (IoT) device, an Internet ofEverything (IoE) device, or an MTC device, or the like, which may beimplemented in various articles such as appliances, vehicles, meters, orthe like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. According to some aspects, M2M communicationor MTC may include communications from devices that integrate sensors ormeters to measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). According to some aspects,half-duplex communications may be performed at a reduced peak rate.Other power conservation techniques for UEs 115 include entering a powersaving “deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 over a sidelink connection (e.g., using a peer-to-peer(P2P) or device-to-device (D2D) protocol). Such communications may bereferred to as D2D or sidelink communications. One or more of a group ofUEs 115 utilizing sidelink communications may be within the geographiccoverage area 110 of a base station 105. In some cases, other UEs 115 insuch a group may be outside the geographic coverage area 110 of a basestation 105 or be otherwise unable to receive transmissions from a basestation 105. In some cases, groups of UEs 115 communicating via sidelinkcommunications may utilize a one-to-many (1:M) system in which each UE115 transmits to every other UE 115 in the group.

In some cases, a base station 105 facilitates the scheduling ofresources for sidelink communications. In other cases, sidelinkcommunications are carried out between UEs 115 without the involvementof a base station 105. According to some aspects, sidelinkcommunications may include discovery expression transmissions on aphysical sidelink discovery channel (PSDCH) (e.g., to allow proximaldevices to discover each other's presence). According to some aspects,sidelink communications may include control information transmissions ona physical sidelink control channel (PSCCH). According to some aspects,sidelink communications may include data transmissions on a physicalsidelink shared channel (PSSCH). According to some aspects, sidelinkcommunications may include feedback transmissions on a physical sidelinkfeedback channel (PSFCH).

According to some aspects, sidelink communications may include LTE V2Xor cellular V2X (C-V2X), NR V2X or C-V2X, and NR sidelink. In NR-V2X,two modes may be defined for resource allocation. In a first mode (e.g.,mode-1), a base station 105 may determine the resources used by asidelink transmit UE 115 for a sidelink transmission (e.g., on a PSCCH,PSSCH, or PSFCH). In a second mode (e.g., mode-2), a sidelink transmitUE (e.g., not the base station 105) may determine the resources to usefor sidelink communications. Sensing and resource selection andreselection related procedures may be supported for the second mode. Thesensing procedure may be defined as decoding the sidelink controlinformation (SCI) from other UEs and or performing sidelinkmeasurements. Decoding SCIs in the sensing procedure may provide atleast some information on sidelink resources indicated by the UE 115transmitting the SCI.

NR-V2X may support an initial transmission of a transport block from asidelink UE 115 without reservation, based on sensing and a resourceselection procedure. NR-V2X may support the reservation of a sidelinkresource for an initial transmission of a transport block at least by anSCI associated with a different transport block, based on sensing and aresource selection procedure. In some cases, NR-V2X mode-2 may supportresource reservation for feedback-based PSSCH retransmissions bysignaling associated with a prior transmission of the same transportblock (e.g., where the feedback may impact subsequent sensing andresource selection procedures). From the perspective of a transmitsidelink UE 115, the use of HARQ feedback for the release of unusedresources may be supported (e.g., with no additional signaling beingdefined for the purpose of the release of unused resources by thetransmit UE 115). Additionally, in mode-2, the SCI payload may indicatethe sub-channels and slots used by a UE 115 or reserved by a UE 115 forPSSCH transmissions or retransmissions.

Base stations 105 may communicate with the core network 130 and with oneanother. According to some aspects, base stations 105 may interface withthe core network 130 through backhaul links 132 (e.g., via an S1, N2,N3, or other interface). Base stations 105 may communicate with oneanother over backhaul links 134 (e.g., via an X2, Xn, or otherinterface) either directly (e.g., directly between base stations 105) orindirectly (e.g., via core network 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 megahertz (MHz) to 300gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known asthe ultra-high frequency (UHF) region or decimeter band, since thewavelengths range from approximately one decimeter to one meter inlength. UHF waves may be blocked or redirected by buildings andenvironmental features. However, the waves may penetrate structuressufficiently for a macro cell to provide service to UEs 115 locatedindoors. Transmission of UHF waves may be associated with smallerantennas and shorter range (e.g., less than 100 km) compared totransmission using the smaller frequencies and longer waves of the highfrequency (HF) or very high frequency (VHF) portion of the spectrumbelow 300 MHz. Wireless communications system 100 may also operate in asuper high frequency (SHF) region using frequency bands from 3 GHz to 30GHz, also known as the centimeter band. The SHF region includes bandssuch as the 5 GHz industrial, scientific, and medical (ISM) bands, whichmay be used opportunistically by devices that may be capable oftolerating interference from other users.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. According to some aspects, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothunshared (e.g., licensed) and shared (e.g., unlicensed) radio frequencyspectrum bands. According to some aspects, wireless communicationssystem 100 may employ License Assisted Access (LAA), LTE-Unlicensed(LTE-U) radio access technology, or NR technology in an unlicensed bandsuch as the 5 GHz ISM band. When operating in unlicensed radio frequencyspectrum bands, wireless devices such as base stations 105 and UEs 115may employ LBT procedures to ensure a frequency channel (e.g., an LBTsubchannel or a frequency band that is accessible via an LBT procedure)is clear before transmitting data. In some cases, operations inunlicensed bands may be based on a carrier aggregation configuration inconjunction with component carriers operating in a licensed band (e.g.,LAA). Operations in unlicensed spectrum may include downlinktransmissions, uplink transmissions, sidelink transmissions,peer-to-peer transmissions, or a combination of these. Duplexing inunlicensed spectrum may be based on frequency division duplexing (FDD),time division duplexing (TDD), or a combination of both.

In some implementations, there may be different categories of LBTprocedures, including category 1 LBT (i.e., no LBT), category 2 LBT(i.e., LBT including one-time channel sensing for a fixed period withouta back-off period), category 3 LBT (i.e., LBT with a random (or other)back-off period and a fixed sized contention window), and category 4 LBT(i.e., LBT with a random (or other) back-off period and a variable sizedcontention window). In some cases, a category 2 LBT procedure may bereferred to as a one-time LBT procedure where a UE 115 may performchannel sensing for a defined duration (e.g., 25 μs). Further, acategory 4 LBT procedure may be referred to as a fairness-based LBTprocedure for performing channel sensing with a backoff, where thebackoff may be used to prevent a UE 115 from accessing a channelimmediately after detecting that the channel is clear.

In some cases, wireless communications system 100 may be a packet-basednetwork that operates according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer mayperform packet segmentation and reassembly to communicate over logicalchannels. A Medium Access Control (MAC) layer may perform priorityhandling and multiplexing of logical channels into transport channels.The MAC layer may also use HARQ to provide retransmission at the MAClayer to improve link efficiency. In the control plane, the RadioResource Control (RRC) protocol layer may provide establishment,configuration, and maintenance of an RRC connection between a UE 115 anda base station 105 or core network 130 supporting radio bearers for userplane data. At the Physical layer, transport channels may be mapped tophysical channels.

In some cases, UEs 115 and base stations 105 may support retransmissionsof data to increase the likelihood that data is received successfully.HARQ feedback is one technique of increasing the likelihood that data isreceived correctly over a communication link 125. HARQ feedback mayinclude an acknowledgement (ACK) indicating that data was received anddecoded successfully or a negative acknowledgement (NACK) indicatingthat data was not received or decoded successfully. HARQ may include acombination of error detection (e.g., using a cyclic redundancy check(CRC)), forward error correction (FEC), and retransmission (e.g.,automatic repeat request (ARQ)). HARQ may improve throughput at the MAClayer in poor radio conditions (e.g., signal-to-noise conditions). Insome cases, a wireless device may support same-slot HARQ feedback, wherethe device may provide HARQ feedback in a specific slot for datareceived in a previous symbol in the slot. In other cases, the devicemay provide HARQ feedback in a subsequent slot, or according to someother time interval.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may refer to a sampling period of T_(s)=1/30,720,000seconds. Time intervals of a communications resource may be organizedaccording to radio frames each having a duration of 10 milliseconds(ms), where the frame period may be expressed as T_(f)=307,200 T_(s).The radio frames may be identified by a system frame number (SFN)ranging from 0 to 1023. Each frame may include 10 subframes numberedfrom 0 to 9, and each subframe may have a duration of 1 ms. A subframemay be further divided into 2 slots each having a duration of 0.5 ms,and each slot may contain 6 or 7 modulation symbol periods (e.g.,depending on the length of the cyclic prefix prepended to each symbolperiod). Excluding the cyclic prefix, each symbol period may contain2048 sampling periods.

In some cases, a subframe may be the smallest scheduling unit of thewireless communications system 100 and may be referred to as atransmission time interval (TTI). In other cases, a smallest schedulingunit of the wireless communications system 100 may be shorter than asubframe or may be dynamically selected (e.g., in bursts of shortenedTTIs (sTTIs) or in selected component carriers using sTTIs). In somewireless communications systems, a slot may further be divided intomultiple mini-slots containing one or more symbols. In some instances, asymbol of a mini-slot or a mini-slot may be the smallest unit ofscheduling. Each symbol may vary in duration depending on the subcarrierspacing or frequency band of operation. Further, some wirelesscommunications systems may implement slot aggregation in which multipleslots or mini-slots are aggregated together and used for communicationbetween a UE 115 and a base station 105.

As mentioned above, wireless communications system 100 may supportsidelink communications between UEs 115 (e.g., introduced in LTE), wherea UE 115 may send data to another UE 115 without tunneling through abase station 105 or core network 130. In some cases, sidelinkcommunications (e.g., D2D or C-V2X) may be performed over an unsharedspectrum (e.g., dedicated spectrum or licensed spectrum), where channelaccess may be straightforward since a base station 105 may haveownership of the spectrum. In other cases, sidelink communications maybe performed over a shared radio frequency spectrum (e.g., in NRunlicensed (NR-U) applications). The shared radio frequency spectrum orshared spectrum may be a spectrum that is unlicensed, licensed tomultiple operators, or licensed to a single operation with opportunisticaccess by other devices (e.g., a licensed radio frequency spectrum, anunlicensed radio frequency spectrum, or a combination of licensed andunlicensed radio frequency spectrum).

NR-U may be targeted to work on the 5 GHz band or the 6 GHz band, wherethere may be well-defined channel access rules while the channel isshared with another operator or even with other radio accesstechnologies (RATs). However, in NR-U, a base station 105 may not havefull ownership or control of the channel, and UEs 115 may contend foraccess to the channel. NR-U may be used for sidelink operation byallowing a UE 115 to transmit to other UEs 115 over a shared spectrumband to offload traffic using a “free” spectrum. In NR-V2X, a resourcepool may be defined for sidelink communications. A resource pool may bea set of time and frequency resources that can be used for sidelinktransmission or reception. From the point of view of a UE 115, aresource pool may be inside the bandwidth allocated for the UE 115 andwithin a sidelink bandwidth part (BWP) and may have a single numerology.The time-domain resources in a resource pool may be non-contiguous(e.g., for NR sidelink in a licensed band), and multiple resource poolsmay be preconfigured to a UE 115 in a carrier.

FIG. 2 illustrates aspects of non-contiguous time-domain resources 200used for sidelink communications in accordance with aspects of thepresent disclosure. According to aspects illustrated in FIG. 2, a UE 115may be scheduled to transmit sidelink data to another UE 115 on a firstresource set 205-a, a second resource set 205-b, and a third resourceset 205-c. If, however, the UE 115 determines to transmit the sidelinkdata in the shared spectrum, the UE 115 may have to gain access to theshared spectrum multiple (e.g., three) times to transmit the sidelinkdata on the different, non-contiguous resource sets. In some cases,after giving up access to the shared spectrum (e.g., after transmittingsidelink data on the first resource set 205-a), the UE 115 may fail toregain access to the shared spectrum (e.g., to transmit on the secondresource set 205-b or the third resource set 205-c). Accordingly, the UE115 may not be able to finish transmitting the sidelink data to theother UE 115, resulting in loss of throughput.

In wireless communications system 100, to improve throughput, thetime-domain resources in a resource pool configured for sidelinkcommunications in a shared spectrum may be contiguous. As such, a UE 115may not have to reacquire access to the shared spectrum multiple timesto transmit sidelink data to another UE 115. In addition, to give otherUEs 115 a chance to access the resource pool, a UE 115 may transmit oninterleaved frequency resources in each time interval of a set ofcontiguous time intervals in the resource pool (e.g., such that theother UEs 115 may access frequency resources not used in the set ofcontiguous time intervals). In some cases, however, the use of the samefrequency resources to transmit sidelink data in multiple time intervalsmay limit transmit diversity, and the throughput gains achieved bytransmitting in contiguous time intervals may be compromised. Further,in some wireless communications systems, a UE 115 may be allowed toreserve resources for retransmissions, and the UE 115 may or may not usethe reserved resources. In such systems, the reservation of unusedresources may be wasteful and may restrict other UEs 115 from accessinga shared spectrum for sidelink communications. As described herein, UEs115 in wireless communications system 100 may support techniques forefficiently selecting resources for sidelink communications in a sharedspectrum while allowing other UEs 115 a chance to gain access to theshared spectrum.

FIG. 3 illustrates aspects of a wireless communications system 300 thatsupports resource configuration and reservation for sidelinkcommunications in accordance with aspects of the present disclosure. Thewireless communications system 300 includes a base station 105-a, whichmay be an example of a base station 105 described with reference toFIGS. 1 and 2. The wireless communications system 300 also includes a UE115-a and a UE 115-b, which may be examples of UEs 115 described withreference to FIGS. 1 and 2. Base station 105-a may providecommunications coverage for geographic coverage area 110-a, which may bean example of a geographic area 110 described with reference to FIG. 1.The wireless communications system 300 may implement aspects of thewireless communications system 100. According to some aspects, UE 115-aand UE 115-b in wireless communications system 300 may supporttechniques for efficiently selecting resources for sidelinkcommunications in a shared spectrum while allowing other UEs 115 achance to gain access to the shared spectrum.

According to aspects illustrated in FIG. 3, the UE 115-a may receive anindication of (or may otherwise identify) a TFRP configuration thatindicates contiguous time intervals (or grids) allocated for sidelinkcommunications in a shared spectrum. The time intervals may start atfixed and common points (e.g., common to all UEs 115, such as at thebeginning of every four time slots) and may span multiple time slots.Each time interval may be configured with small gaps within which otherUEs 115 may perform LBT procedures to gain access to the sharedspectrum. Before UE 115-a transmits sidelink data to UE 115-b in theshared spectrum, the base station 105-a may transmit downlink controlinformation (DCI) or the UE 115-a may transmit SCI indicating theremaining usable interlaces for other UEs 115, a time when channelaccess will end, etc. Then, as described herein, rather thantransmitting the sidelink data on the same interlaced frequencyresources across multiple time intervals, UE 115-a may select interlacedfrequency resources that frequency hop across time intervals to transmitthe sidelink data to UE 115-b to randomize interference and improvethroughput.

FIG. 4 illustrates aspects of interleaved frequency resources 400 usedfor sidelink communications in contiguous time-domain resources inaccordance with aspects of the present disclosure. The terms interleavedfrequency resources and interlaced frequency resources may be usedinterchangeably herein and may refer to non-contiguous frequencyresources arranged in a comb-like structure (e.g., evenly spaced,non-contiguous frequency resources). The use of contiguous time-domainresources for sidelink communications may be described as a case ofresource reservation for transmissions or retransmissions of the sametransport block or different transport blocks with no gap between thetransmissions or retransmissions (e.g., or having gaps smaller than aminimum gap for LBT access by a different device). According to aspectsillustrated in FIG. 4, UE 115-a may gain access to a shared spectrum fora channel occupancy time (COT), and the UE 115-a may transmit sidelinkdata 415 to UE 115-b in the COT. In particular, the UE 115-a maytransmit the sidelink data 415 on a first set of interleaved (i.e.,interlaced) frequency resources in a first time interval 405-a, a secondset of interleaved (i.e., interlaced) frequency resources in a secondtime interval 405-b, and a third set of interleaved (i.e., interlaced)frequency resources in a third time interval 405-c.

Thus, the different sets of interleaved frequency resources used totransmit sidelink data 415 may frequency hop across multiple timeintervals 405. The set of interleaved frequency resources selected ineach time interval 405 may be associated with an interlace index and maybe one set of a number of different sets of interleaved frequencyresources each corresponding to a different interlace index. In somecases, the UE 115-a may transmit SCI 410, or the base station 105-a maytransmit DCI 410, indicating the resources used by UE 115-a to transmitthe sidelink data 415 to UE 115-b. Thus, other UEs 115 may decode theSCI or DCI 410 to determine the resources being used by UE 115-a and toidentify unused resources 420 available for sidelink communications. Inother cases, the resources used by UE 115-a to transmit the sidelinkdata 415 may be preconfigured, and other UEs 115 may identify the unusedresources 420 based on one or more factors as described in furtherdetail below.

According to some aspects, COT sharing may be done per time interval405, and the SCI or DCI 410 in each time interval 405 may indicate theavailable or unused time and frequency resources in the time interval405 (e.g., unused resources 420). For instance, the SCI or DCI 410 inthe first time interval 405-a may indicate the first set of interleavedfrequency resources used by UE 115-a in one or more time slots of thefirst time interval 405-a, and other UEs 115 may determine the unusedresources 420 in the first time interval 405-a based on decoding the SCIor DCI 410 in the first time interval 405-a. For these aspects, becausethe other UEs 115 may have to decode the SCI or DCI 410 at the beginningof a time interval 405 before transmitting in the time interval 405, COTsharing may not be maximized. That is, the other UEs 115 may stoptransmitting in a COT and may not rejoin the COT in a time interval 405until the UE 115 has decoded the DCI or SCI 410 in the time interval405.

According to some aspects, COT sharing may be done across time intervals405, and the SCI or DCI 410 in each time interval 405 may indicate theavailable or unused time and frequency resources in a next time interval405 following the time interval 405 (e.g., unused resources 420). Forinstance, the SCI or DCI 410 in the first time interval 405-a mayindicate the second set of interleaved frequency resources used by UE115-a in one or more time slots of the second time interval 405-b, andother UEs 115 may determine the unused resources 420 in the second timeinterval 405-b based on decoding the SCI or DCI 410 in the first timeinterval 405-a. Thus, within each time grid, the SCI or DCI 410 mayindicate unused interlaces for the next time grid. In some cases, theSCI or DCI 410 in a previous time interval 405 may also indicate whenthe gaps in a next time interval 405 are budgeted for other UEs 115 toperform LBT procedures to gain access to the unused resources 420 in thenext time interval 405. In such cases, the UE 115-a may stoptransmitting in the next time interval 405 during the gaps to preventmutual blocking (e.g., to avoid blocking the other UEs 115 fromaccessing the unused resources 420). As such, the short gaps may allowUE 115-a to share a COT with other UEs 115 (e.g., on interlace indicesor frequency resources that are not used by UE 115-a).

According to some aspects, COT sharing may be done per time interval 405or across time intervals 405, and the SCI or DCI 410 may indicate thefrequency hopping pattern used by UE 115-a to transmit the sidelink data415 across the multiple time intervals 405. For instance, the SCI or DCI410 in the first, second, or third time interval 405 or in a previoustime interval 405 may indicate the frequency hopping patterncorresponding to the first, second, and third sets of interleavedfrequency resources used by UE 115-a to transmit the sidelink data 415in the first, second, and third time intervals 405. That is, the SCI orDCI 410 may indicate a virtual interlace index of a set of virtualinterlace indices, where each virtual interlace index indicates a set ofinterlace indices used by UE 115-a across multiple time intervals 405,and each interlace index identifies a set of interleaved frequencyresources in a respective time interval 405.

According to some aspects, the frequency hopping pattern may bepreconfigured (e.g., the group hopping or sequence hopping from theuplink demodulation reference signal (DMRS) hopping pattern may beadapted for sidelink transmissions). In any case, regardless of whetherthe frequency hopping pattern is preconfigured or indicated in SCI orDCI 410, each interlace index within each time interval 405 indicated bythe frequency hopping pattern may depend on one or more factors. Forinstance, each interlace index within each time interval 405 thatcorresponds to the set of interleaved frequency resources used by UE115-a in the time interval 405 may be a function of one or more factors,including a subcarrier spacing of the time interval 405, a sidelink IDof UE 115-a, a pool ID associated with the resources used by UE 115-a,or some higher layer parameters associated with group hopping (e.g.,received in higher layer signaling used to enable or disable grouphopping). If the frequency hopping pattern is preconfigured, other UEs115 may determine the frequency hopping pattern used by UE 115-a totransmit the sidelink data 415 based on the one or more factors.

Once another UE 115 receives the SCI or DCI 410 indicating the set ofinterleaved frequency resources or otherwise identifies the set ofinterleaved frequency resources used by UE 115-a to transmit sidelinkdata 415 to UE 115-b, the other UE 115 may identify the unused resources420 and may contend for access to the unused resources 420 for sidelinkcommunications. In particular, the other UE 115 may identify a differentset of interleaved frequency resources in a time interval 405 from theset of interleaved frequency resources used by UE 115-a, where thedifferent set of interleaved frequency resources may correspond to adifferent frequency hopping pattern from the frequency hopping patternused by UE 115-a. The other UE 115 may then transmit sidelink dataacross one or more time intervals 405 based on the different frequencyhopping pattern (e.g., including at least transmitting the sidelink dataon the different set of interleaved frequency resources in the timeinterval 405).

In addition to the techniques described above, in some cases, it may beappropriate for a UE 115 to release reserved, unused resources to allowother UEs 115 to gain access to a shared spectrum. In particular,because a UE 115 may reserve resources for a retransmission after aninitial transmission (e.g., using signaling associated with the initialtransmission), and the UE 115 may receive feedback indicating that theinitial transmission was received successfully before theretransmission, the reservation of the resources for the retransmissionmay be underutilized.

As described herein, a UE 115 may be configured to release resourcesreserved for a retransmission of a transport block after receivingfeedback indicating that a previous transmission of the transport blockwas successfully received. In addition, other UEs 115 may be configuredto use the released resources after receiving the feedback indicatingthat the initial transmission of the transport block from the UE 115 wassuccessfully received. That is, the other UEs 115 may rely on HARQfeedback to determine when reserved resources are released, and theother UEs 115 may use the released resources for sidelinkcommunications. In some aspects, when a first UE 115 receives a feedbackmessage indicating that a transmission from a second UE 115 wassuccessfully received by a third UE 115, the first UE 115 may useresources reserved by the second UE 115 (e.g., for a subsequentretransmission) to transmit sidelink data to a fourth UE 115 (e.g., thesecond UE 115 may release the reserved, unused resources). Thus, forreservation of a COT with feedback-based PSSCH transmissions orretransmissions, an ACK sent by the third UE 115 (e.g., a receive UE115) in a PSFCH may indicate to the first UE 115 (e.g., and other UEs115) that the reservation is done and the rest of the COT can be shared.

In some cases, the SCI or DCI transmitted by the second UE 115 before atransmission of sidelink data may indicate whether the first UE 115(e.g., and other UEs 115) may monitor a PSFCH to determine whether toaccess resources reserved for a retransmission of the data. That is, theSCI or DCI may indicate whether PSFCH may be used as an indication forCOT sharing. If the SCI or DCI indicates that PSFCH may be used as anindication for COT sharing, the first UE 115 (e.g., and other UEs 115)may access the resources reserved for a retransmission by the second UE115 after receiving an ACK on the PSFCH. In particular, other transmitUEs 115 may receive an indication (e.g., configured by SCI or DCI of thesecond UE 115) of when the UEs 115 are eligible to join or accessresources reserved for a retransmission. In some aspects, the othertransmit UEs 115 may be eligible to join or access resources reservedfor a retransmission (e.g., using a category 2 LBT procedure) one slotafter the slot (e.g., slot n) in which an ACK is received (e.g., fromthe third UE 115) or soon after receiving the ACK on the PSFCH.

FIG. 5 illustrates aspects of a process flow 500 that supports resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure. The process flow 500 illustratesaspects of techniques performed by a UE 115-c, a UE 115-d, and a UE115-e, which may be examples of a UE 115 described with reference toFIGS. 1-4. In FIG. 5, the UE 115-c may receive (or otherwise identify) aresource pool configuration indicating resources in a shared radiofrequency spectrum band available to the UE 115-c for sidelinkcommunications, where the resources include contiguous time intervals.

At 505, UE 115-c may perform an LBT procedure to gain access to theshared spectrum band for a COT to transmit sidelink data to UE 115-e.The COT may span one or more contiguous time intervals of the contiguoustime intervals indicated by the resource pool configuration. At 510, UE115-c may identify a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting the sidelink data in afirst time interval and a second set of interleaved frequency resourcesfor transmitting the sidelink data in a second time interval. That is,if the LBT procedure is successful, the UE 115-c may reserve resourcesfor transmitting the sidelink data based on the frequency hoppingpattern.

At 515, UE 115-c may transmit SCI in the first time interval with thesidelink data on at least a subset of the first set of interleavedfrequency resources. The SCI may indicate the first set of interleavedfrequency resources being used by the UE 115-c to transmit the sidelinkdata to the UE 115-e. According to some aspects, when sidelinkcommunications are scheduled by a base station 105 (e.g., rather than bythe UE 115-c), the base station 105 may transmit DCI to UE 115-c, UE115-d, and UE 115-e indicating the first set of interleaved frequencyresources being used by the UE 115-c to transmit the sidelink data tothe UE 115-e (e.g., the UE 115-c may not transmit the SCI). At 520, theUE 115-c may then transmit the sidelink data to UE 115-e in the firsttime interval on the first set of interleaved frequency resources.

At 525, UE 115-c may transmit SCI in the second time interval with thesidelink data on at least a subset of the second set of interleavedfrequency resources. The SCI may indicate the second set of interleavedfrequency resources being used by the UE 115-c to transmit the sidelinkdata to the UE 115-e. According to some aspects, when sidelinkcommunications are scheduled by a base station 105 (e.g., rather than bythe UE 115-c), the base station 105 may transmit DCI to UE 115-c, UE115-d, and UE 115-e indicating the second set of interleaved frequencyresources being used by the UE 115-c to transmit the sidelink data tothe UE 115-e (e.g., the UE 115-c may not transmit the SCI). At 530, theUE 115-c may then transmit the sidelink data to UE 115-e in the secondtime interval on the second set of interleaved frequency resources. Insome cases, UE 115-c may also transmit an indication of gaps in thefirst time interval, the second time interval, or both allocated forother UEs (e.g., UE 115-d) to perform LBT procedures to gain access tothe shared spectrum.

As described above, the UE 115-c may transmit the SCI and the sidelinkdata to UE 115-e, but the resources used to transmit the SCI and thesidelink data may be monitored by UE 115-d. That is, the UE 115-d maymonitor the pool of resources configured for sidelink communications ina shared spectrum. Thus, when the UE 115-d identifies data to transmitto another UE 115, the UE 115-d may decode the SCI to identify if otherUEs 115 have reserved resources of the shared spectrum band for sidelinkcommunications. Alternatively, the UE 115-d may decode DCI to identifyif other UEs 115 have reserved resources of the shared spectrum band forsidelink communications (e.g., if sidelink communications are scheduledby a base station 105). Although FIG. 5 illustrates that the UE 115-dmay receive SCI from the UE 115-c to identify resources being used bythe UE 115-c for sidelink communications, it is to be understood thatthe UE 115-d may receive and decode DCI to identify resources being usedby the UE 115-c for sidelink communications. Thus, SCI and DCI may beused interchangeably in some aspects described herein.

According to aspects illustrated in FIG. 5, UE 115-d may identify, fromthe SCI, that UE 115-c has reserved the shared spectrum for sidelinkcommunications in the COT. UE 115-d may then identify, from the SCI, atleast one set of interleaved frequency resources that is available for atime interval. That is, the SCI at 515 or the SCI at 525 may indicatethe at least one set of interleaved frequency resources that isavailable for the time interval. The at least one set of interleavedfrequency resources may be one of multiple sets of interleaved frequencyresources that frequency hop between time intervals based on respectivefrequency hopping patterns. UE 115-d may perform an LBT procedure (e.g.,category 2 LBT) for the available set of interleaved frequency resourcesand may transmit to another UE 115 over the set of interleaved frequencyresources if the LBT procedure is successful (not shown).

According to some aspects, the SCI in the first time interval mayindicate the first set of interleaved frequency resources used by UE115-c to transmit the sidelink data in the first time interval, and theSCI in the second time interval may indicate the second set ofinterleaved frequency resources used by UE 115-c to transmit thesidelink data in the second time interval. In such cases, UE 115-d mayidentify a set of interleaved frequency resources that is available forthe first time interval after decoding the SCI received at the beginningof the first time interval, and UE 115-d may identify a set ofinterleaved frequency resources that is available for the second timeinterval after decoding the SCI received at the beginning of the secondtime interval.

According to some aspects, the SCI in a previous time interval mayindicate the first set of interleaved frequency resources used by UE115-c to transmit the sidelink data in the first time interval, and theSCI in the first time interval may indicate the second set ofinterleaved frequency resources used by UE 115-c to transmit thesidelink data in the second time interval. In such cases, UE 115-d mayidentify a set of interleaved frequency resources that is available forthe first time interval after decoding the SCI received in the previoustime interval (e.g., in advance of the first time interval), and UE115-d may identify a set of interleaved frequency resources that isavailable for the second time interval after decoding the SCI receivedin the first time interval (e.g., in advance of the second timeinterval).

According to some aspects, the SCI in the first time interval, thesecond time interval, or a previous time interval may indicate afrequency hopping pattern used by UE 115-c to transmit the sidelink dataon the first set of interleaved frequency resources in the first timeinterval and the second set of interleaved frequency resources in thesecond time interval. In such cases, UE 115-d may identify a set ofinterleaved frequency resources that is available for the first timeinterval after decoding the SCI received in the first time interval orSCI received in a previous time interval (e.g., indicating the frequencyhopping pattern used by UE 115-c), and UE 115-d may identify a set ofinterleaved resources that is available for the second time intervalafter decoding the SCI received in the second time interval or SCIreceived in a previous time interval (e.g., indicating the frequencyhopping pattern used by UE 115-c).

According to some aspects, the first set of interleaved frequencyresources used by UE 115-c in the first time interval and the second setof interleaved frequency resources used by UE 115-c in the second timeinterval may be preconfigured (e.g., in the resource poolconfiguration). In some aspects, respective sets of interleavedfrequency resources in each time interval may be based one or morefactors, such as a subcarrier spacing of the time interval, a sidelinkID of UE 115-c, a resource pool ID of the respective set of interleavedfrequency resources, or one or more parameters associated with grouphopping of frequency resources. In such cases, UE 115-d may identify aset of interleaved frequency resources that is available for the firsttime interval after determining that UE 115-c is using the first set ofinterleaved frequency resources in the first time interval based on theone or more factors, and UE 115-d may identify a set of interleavedfrequency resources that is available for the second time interval afterdetermining that UE 115-c is using the second set of interleavedfrequency resources in the second time interval based on the one or morefactors.

The set of interleaved frequency resources available in the first timeinterval may be different from (e.g., non-overlapping with) the firstset of interleaved frequency resources, and the set of interleavedfrequency resources available in the second time interval may bedifferent from (e.g., non-overlapping with) the second set ofinterleaved frequency resources. Thus, when UE 115-d identifies theavailable set of interleaved frequency resources in the first timeinterval, UE 115-d may perform an LBT procedure to gain access to theavailable set of interleaved frequency resources and may transmitsidelink data to another UE 115 on the available set of interleavedfrequency resources in the first time interval. Additionally, oralternatively, when UE 115-d identifies the available set of interleavedfrequency resources in the second time interval, UE 115-d may perform anLBT procedure to gain access to the available set of interleavedfrequency resources and may transmit sidelink data to another UE 115 onthe available set of interleaved frequency resources in the second timeinterval (not shown).

FIG. 6 illustrates aspects of a process flow 600 that supports resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure. The process flow 600 illustratesaspects of techniques performed by a UE 115-f, a UE 115-g, a UE 115-h,and a UE 115-i, which may be examples of a UE 115 described withreference to FIGS. 1-5.

At 605, UE 115-g may identify that UE 115-h has reserved a sharedspectrum for sidelink communications in a COT spanning a set ofcontiguous time intervals. At 610, UE 115-h may transmit sidelink datato UE 115-i, and, at 615, UE 115-h may receive an ACK for the sidelinkdata transmitted at 610. As illustrated by aspects of FIG. 6, though UE115-i may transmit the ACK to UE 115-h, the resources used to transmitthe ACK may be monitored by UE 115-g. That is, the UE 115-g may monitorthe pool of resources configured for sidelink communications in a sharedspectrum. Thus, UE 115-g may receive the ACK transmitted by UE 115-i at615, and, at 620, UE 115-g may identify resources reserved for aretransmission of the sidelink data transmitted at 610.

At 625, UE 115-g may then initiate an LBT procedure to gain access tothe identified resources for at least one interval of the COT. At 630,UE 115-g may transmit, based on a result of the LBT procedure, sidelinkdata to UE 115-f on the identified resources based on receiving the ACKtransmitted by UE 115-i. That is, because the sidelink data transmittedat 610 may be successfully received by the UE 115-i, the UE 115-h maynot use the resources reserved for retransmission of the sidelink data.Thus, the UE 115-g may identify the resources that are unused by the UE115-h, and the UE 115-g may transmit sidelink data to the UE 115-f onthe resources.

In some cases, UE 115-g may receive control information (e.g., SCI fromUE 115-g or DCI from a base station 105) indicating that the resourcesreserved for the retransmission are released by UE 115-h upon UE 115-iacknowledging receipt of the transmission of sidelink data at 610. Thecontrol information may indicate a quantity of slots after receiving theACK that UE 115-g is to wait before transmitting the sidelink data at630 on the resources reserved for the retransmission. The controlinformation may also indicate that UE 115-g is eligible to transmitusing the identified resources for the at least one interval of the COT.

FIG. 7 shows a block diagram 700 of a device 705 that supports resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure. The device 705 may be an exampleof aspects of a UE 115 as described herein. The device 705 may include areceiver 710, a communications manager 715, and a transmitter 720. Thedevice 705 may also include a processor. Each of these components may bein communication with one another (e.g., via one or more buses).

The receiver 710 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to resourceconfiguration and reservation for sidelink communications, etc.).Information may be passed on to other components of the device 705. Thereceiver 710 may be an example of aspects of the transceiver 1020described with reference to FIG. 10. The receiver 710 may utilize asingle antenna or a set of antennas.

The communications manager 715 may be implemented as an integratedcircuit or chipset for the device 705, and the receiver 710 and thetransmitter 720 may be implemented as analog components (for example,amplifiers, filters, antennas) coupled with the device 705 modem toenable wireless transmission and reception. The actions performed by thecommunications manager 715 as described herein may be implemented torealize one or more potential advantages. At least one implementationmay enable the communications manager 715 to efficiently selectresources for sidelink communications in a shared spectrum whileallowing other UEs a chance to gain access to the shared spectrum.Because the resources selected for sidelink communications may includeinterleaved frequency resources, one or more processors of the device705 (for example, processor(s) controlling or incorporated with thecommunications manager 715) may experience power savings (e.g.,increased battery life) since the UE may reliably transmit sidelinkdata, and the UE may avoid reacquiring access to the shared spectrum fora retransmission of the sidelink data.

The communications manager 715 may identify a resource poolconfiguration indicating resources in a shared radio frequency spectrumband available to the first UE for sidelink communications, theresources comprising a plurality of contiguous time intervals, identifya frequency hopping pattern including a first set of interleavedfrequency resources for transmitting sidelink data in a first timeinterval of the set of contiguous time intervals and a second set ofinterleaved frequency resources for transmitting the sidelink data in asecond time interval of the set of contiguous time intervals, andtransmit, to a second UE, the sidelink data on the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern.

The communications manager 715 may also identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receive control informationindicating at least one set of interleaved frequency resources that isavailable for a time interval of the set of contiguous time intervals,the at least one set of interleaved frequency resources being one of aset of sets of interleaved frequency resources that frequency hopbetween time intervals based on respective frequency hopping patterns,and transmit, to a third UE, sidelink data in the time interval on theat least one set of interleaved frequency resources.

The communications manager 715 may also identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receive a feedback messagetransmitted by a third UE acknowledging receipt of a transmission offirst sidelink data from the second UE, identify resources reserved fora retransmission of the first sidelink data from the second UE to thethird UE, initiate a listen-before-talk procedure to gain access to theidentified resources for at least one interval of the channel occupancytime, and transmit, based on a result of the listen-before-talkprocedure, second sidelink data to a fourth UE on the identifiedresources based on receiving the feedback message. The communicationsmanager 715 may be an example of aspects of the communications manager1010 described herein.

The communications manager 715, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 715, or itssub-components may be executed by a general-purpose processor, a DSP, anapplication-specific integrated circuit (ASIC), a FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The communications manager 715, or its sub-components, may be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations byone or more physical components. According to some aspects, thecommunications manager 715, or its sub-components, may be a separate anddistinct component in accordance with various aspects of the presentdisclosure. According to some aspects, the communications manager 715,or its sub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

The transmitter 720 may transmit signals generated by other componentsof the device 705. According to some aspects, the transmitter 720 may becollocated with a receiver 710 in a transceiver module. According tosome aspects, the transmitter 720 may be an example of aspects of thetransceiver 1020 described with reference to FIG. 10. The transmitter720 may utilize a single antenna or a set of antennas.

FIG. 8 shows a block diagram 800 of a device 805 that supports resourceconfiguration and reservation for sidelink communications in accordancewith aspects of the present disclosure. The device 805 may be an exampleof aspects of a device 705, or a UE 115 as described herein. The device805 may include a receiver 810, a communications manager 815, and atransmitter 850. The device 805 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

The receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to resourceconfiguration and reservation for sidelink communications, etc.).Information may be passed on to other components of the device 805. Thereceiver 810 may be an example of aspects of the transceiver 1020described with reference to FIG. 10. The receiver 810 may utilize asingle antenna or a set of antennas.

The communications manager 815 may be an example of aspects of thecommunications manager 715 as described herein. The communicationsmanager 815 may include an LBT manager 820, a frequency hopping manager825, a sidelink manager 830, a shared spectrum manager 835, a feedbackmanager 840, and a resource identifier 845. The communications manager815 may be an example of aspects of the communications manager 1010described herein.

The sidelink manager 830 may receive a resource pool configurationindicating resources in a shared radio frequency spectrum band availableto the first UE for sidelink communications, the resources comprising aplurality of contiguous time intervals. For example, the sidelinkmanager 830 may receive the resource pool configuration from a basestation (e.g., via RRC signaling). The frequency hopping manager 825 mayidentify a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting sidelink data in afirst time interval of the set of contiguous time intervals and a secondset of interleaved frequency resources for transmitting the sidelinkdata in a second time interval of the set of contiguous time intervals.The sidelink manager 830 may transmit, to a second UE, the sidelink dataon the first set of interleaved frequency resources in the first timeinterval and the second set of interleaved frequency resources in thesecond time interval based on the frequency hopping pattern.

The shared spectrum manager 835 may identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals. The frequency hoppingmanager 825 may receive control information indicating at least one setof interleaved frequency resources that is available for a time intervalof the set of contiguous time intervals, the at least one set ofinterleaved frequency resources being one of a set of sets ofinterleaved frequency resources that frequency hop between timeintervals based on respective frequency hopping patterns. The sidelinkmanager 830 may transmit, to a third UE, sidelink data in the timeinterval on the at least one set of interleaved frequency resources.

The shared spectrum manager 835 may identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals. The feedback manager 840may receive a feedback message transmitted by a third UE acknowledgingreceipt of a transmission of first sidelink data from the second UE. Theresource identifier 845 may identify resources reserved for aretransmission of the first sidelink data from the second UE to thethird UE. The LBT manager 820 may initiate a listen-before-talkprocedure to gain access to the identified resources for at least oneinterval of the channel occupancy time. The sidelink manager 830 maytransmit, based on a result of the listen-before-talk procedure, secondsidelink data to a fourth UE on the identified resources based onreceiving the feedback message.

The transmitter 850 may transmit signals generated by other componentsof the device 805. According to some aspects, the transmitter 850 may becollocated with a receiver 810 in a transceiver module. According tosome aspects, the transmitter 850 may be an example of aspects of thetransceiver 1020 described with reference to FIG. 10. The transmitter850 may utilize a single antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a communications manager 905 thatsupports resource configuration and reservation for sidelinkcommunications in accordance with aspects of the present disclosure. Thecommunications manager 905 may be an example of aspects of acommunications manager 715, a communications manager 815, or acommunications manager 1010 described herein. The communications manager905 may include an LBT manager 910, a frequency hopping manager 915, asidelink manager 920, a control information manager 925, a sharedspectrum manager 930, a feedback manager 935, and a resource identifier940. Each of these modules may communicate, directly or indirectly, withone another (e.g., via one or more buses).

The sidelink manager 920 may identify a resource pool configurationindicating resources in a shared radio frequency spectrum band availableto the first UE for sidelink communications, the resources comprising aplurality of contiguous time intervals. For example, the sidelinkmanager 920 may receive the resource pool configuration from a basestation (e.g., via RRC signaling). The frequency hopping manager 915 mayidentify a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting sidelink data in afirst time interval of the set of contiguous time intervals and a secondset of interleaved frequency resources for transmitting the sidelinkdata in a second time interval of the set of contiguous time intervals.The sidelink manager 920 may transmit, to a second UE, the sidelink dataon the first set of interleaved frequency resources in the first timeinterval and the second set of interleaved frequency resources in thesecond time interval based on the frequency hopping pattern.

According to some aspects, the LBT manager 910 may perform alisten-before-talk procedure to gain access to the shared radiofrequency spectrum band for a channel occupancy time to transmit thesidelink data to the second UE, the channel occupancy time spanning atleast the first time interval and the second time interval of theplurality of contiguous time intervals. The control information manager925 may receive control information indicating at least one set ofinterleaved frequency resources that is available for each time intervalof the plurality of contiguous time intervals, and the frequency hoppingmanager 915 may identify the frequency hopping pattern including thefirst set of interleaved frequency resources in the first time intervaland the second set of interleaved frequency resources in the second timeinterval based at least in part on receiving the control information.

The control information manager 925 may transmit, in the first timeinterval, an indication of the first set of interleaved frequencyresources used for transmitting the sidelink data in the first timeinterval. According to some aspects, the control information manager 925may transmit, in the second time interval, an indication of the secondset of interleaved frequency resources used for transmitting thesidelink data in the second time interval. According to some aspects,the control information manager 925 may transmit, in the first timeinterval, an indication of the second set of interleaved frequencyresources used for transmitting the sidelink data in the second timeinterval. According to some aspects, the control information manager 925may transmit, in the first time interval, the second time interval, orboth, an indication of the frequency hopping pattern used by the firstUE to transmit sidelink data on the first set of interleaved frequencyresources in the first time interval and on the second set ofinterleaved frequency resources in the second time interval.

According to some aspects, the control information manager 925 maytransmit an indication of gaps in the first time interval, the secondtime interval, or both, allocated for other UEs to performlisten-before-talk procedures to gain access to the shared radiofrequency spectrum band. In some cases, respective sets of interleavedfrequency resources in each time interval of the set of contiguous timeintervals are based on a subcarrier spacing of the time interval, asidelink ID of the first UE, a resource pool ID of the respective set ofinterleaved frequency resources, one or more parameters associated withgroup hopping of frequency resources, or a combination thereof.

The shared spectrum manager 930 may identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals. According to some aspects,the frequency hopping manager 915 may receive control informationindicating at least one set of interleaved frequency resources that isavailable for a time interval of the set of contiguous time intervals,the at least one set of interleaved frequency resources being one of aset of sets of interleaved frequency resources that frequency hopbetween time intervals based on respective frequency hopping patterns.According to some aspects, the sidelink manager 920 may transmit, to athird UE, sidelink data in the time interval on the at least one set ofinterleaved frequency resources.

In some cases, the control information is received in the time interval,the control information including an indication of a set of interleavedfrequency resources reserved by the second UE for sidelinkcommunications in the time interval. In some cases, the time interval isa first time interval and the control information is received in asecond time interval preceding the first time interval, the controlinformation including an indication of a set of interleaved frequencyresources reserved by the second UE for sidelink communications in thefirst time interval. In some cases the control information includes anindication of a frequency hopping pattern used by the second UE forsidelink communications in the channel occupancy time, and the frequencyhopping manager 915 may identify the at least one set of interleavedfrequency resources for the time interval based on the frequency hoppingpattern.

According to some aspects, the LBT manager 910 may receive an indicationof gaps in the time interval allocated for the first UE to perform alisten-before-talk procedure. According to some aspects, the LBT manager910 may initiate the listen-before-talk procedure in at least one of theindicated gaps to gain access to the shared radio frequency spectrumband to transmit the sidelink data based on the receiving. In somecases, a respective set of interleaved frequency resources reserved bythe second UE for sidelink communications in each time interval of theset of contiguous time intervals is based on a subcarrier spacing of thetime interval, a sidelink identification (ID) of the second UE, aresource pool ID of the respective set of interleaved frequencyresources, higher layer parameters to enable or disable group hopping,or a combination thereof.

According to some aspects, the shared spectrum manager 930 may identifythat a second UE has reserved a shared radio frequency spectrum band forsidelink communications in a channel occupancy time, the channeloccupancy time spanning a set of contiguous time intervals. The feedbackmanager 935 may receive a feedback message transmitted by a third UEacknowledging receipt of a transmission of first sidelink data from thesecond UE. The resource identifier 940 may identify resources reservedfor a retransmission of the first sidelink data from the second UE tothe third UE. According to some aspects, the LBT manager 910 mayinitiate a listen-before-talk procedure to gain access to the identifiedresources for at least one interval of the channel occupancy time.According to some aspects, the sidelink manager 920 may transmit, basedon a result of the listen-before-talk procedure, second sidelink data toa fourth UE on the identified resources based on receiving the feedbackmessage.

According to some aspects, the control information manager 925 mayreceive control information indicating that the resources reserved forthe retransmission are released upon the third UE acknowledging receiptof the transmission of the first sidelink data. In some cases, thecontrol information further indicates a quantity of slots afterreceiving the feedback message that the first UE is to wait beforetransmitting the second sidelink data on the resources reserved for theretransmission. In some cases, the control information further indicatesthat the first UE is eligible to transmit using the identified resourcesfor the at least one interval of the channel occupancy time. In somecases, the control information includes sidelink control information ordownlink control information.

FIG. 10 shows a diagram of a system 1000 including a device 1005 thatsupports resource configuration and reservation for sidelinkcommunications in accordance with aspects of the present disclosure. Thedevice 1005 may be an example of or include the components of device705, device 805, or a UE 115 as described herein. The device 1005 mayinclude components for bi-directional voice and data communicationsincluding components for transmitting and receiving communications,including a communications manager 1010, an I/O controller 1015, atransceiver 1020, an antenna 1025, memory 1030, and a processor 1040.These components may be in electronic communication via one or morebuses (e.g., bus 1045).

The communications manager 1010 may perform a listen-before-talkprocedure to gain access to a shared radio frequency spectrum band for achannel occupancy time to transmit sidelink data to a second UE, thechannel occupancy time spanning a set of contiguous time intervals,identify a frequency hopping pattern including a first set ofinterleaved frequency resources for transmitting the sidelink data in afirst time interval of the set of contiguous time intervals and a secondset of interleaved frequency resources for transmitting the sidelinkdata in a second time interval of the set of contiguous time intervals,and transmit, to the second UE, the sidelink data on the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern.

The communications manager 1010 may also identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receive control informationindicating at least one set of interleaved frequency resources that isavailable for a time interval of the set of contiguous time intervals,the at least one set of interleaved frequency resources being one of aset of sets of interleaved frequency resources that frequency hopbetween time intervals based on respective frequency hopping patterns,and transmit, to a third UE, sidelink data in the time interval on theat least one set of interleaved frequency resources.

The communications manager 1010 may also identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a set of contiguous time intervals, receive a feedback messagetransmitted by a third UE acknowledging receipt of a transmission offirst sidelink data from the second UE, identify resources reserved fora retransmission of the first sidelink data from the second UE to thethird UE, initiate a listen-before-talk procedure to gain access to theidentified resources for at least one interval of the channel occupancytime, and transmit, based on a result of the listen-before-talkprocedure, second sidelink data to a fourth UE on the identifiedresources based on receiving the feedback message.

The I/O controller 1015 may manage input and output signals for thedevice 1005. The I/O controller 1015 may also manage peripherals notintegrated into the device 1005. In some cases, the I/O controller 1015may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 1015 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 1015may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 1015may be implemented as part of a processor. In some cases, a user mayinteract with the device 1005 via the I/O controller 1015 or viahardware components controlled by the I/O controller 1015.

The transceiver 1020 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. According to someaspects, the transceiver 1020 may represent a wireless transceiver andmay communicate bi-directionally with another wireless transceiver. Thetransceiver 1020 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1025.However, in some cases the device may have more than one antenna 1025,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1030 may include RAM and ROM. The memory 1030 may storecomputer-readable, computer-executable code 1035 including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein. In some cases, the memory 1030 may contain, amongother things, a BIOS which may control basic hardware or softwareoperation such as the interaction with peripheral components or devices.

The processor 1040 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1040 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into the processor 1040. The processor 1040 may beconfigured to execute computer-readable instructions stored in a memory(e.g., the memory 1030) to cause the device 1005 to perform variousfunctions (e.g., functions or tasks supporting resource configurationand reservation for sidelink communications).

The code 1035 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1035 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1035 may not be directly executable by theprocessor 1040 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 11 shows a flowchart illustrating a method 1100 that supportsresource configuration and reservation for sidelink communications inaccordance with aspects of the present disclosure. The operations ofmethod 1100 may be implemented by a UE 115 or its components asdescribed herein. According to some aspects, the operations of method1100 may be performed by a communications manager as described withreference to FIGS. 7 through 10. According to some aspects, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described below. Additionally, oralternatively, a UE may perform aspects of the functions described belowusing special-purpose hardware.

At 1105, the UE may identify a resource pool configuration indicatingresources in a shared radio frequency spectrum available to the first UEfor sidelink communications, the resources comprising a plurality ofcontiguous time intervals. For example, the UE may receive the resourcepool configuration from a base station (e.g., via RRC signaling). Theoperations of 1105 may be performed according to the methods describedherein. According to some aspects, aspects of the operations of 1105 maybe performed by a sidelink manager as described with reference to FIGS.7 through 10.

At 1110, the UE may identify a frequency hopping pattern including afirst set of interleaved frequency resources for transmitting sidelinkdata in a first time interval of the set of contiguous time intervalsand a second set of interleaved frequency resources for transmitting thesidelink data in a second time interval of the set of contiguous timeintervals. The operations of 1110 may be performed according to themethods described herein. According to some aspects, aspects of theoperations of 1110 may be performed by a frequency hopping manager asdescribed with reference to FIGS. 7 through 10.

At 1115, the UE may transmit, to a second UE, the sidelink data on thefirst set of interleaved frequency resources in the first time intervaland the second set of interleaved frequency resources in the second timeinterval based on the frequency hopping pattern. The operations of 1115may be performed according to the methods described herein. According tosome aspects, aspects of the operations of 1115 may be performed by asidelink manager as described with reference to FIGS. 7 through 10.

FIG. 12 shows a flowchart illustrating a method 1200 that supportsresource configuration and reservation for sidelink communications inaccordance with aspects of the present disclosure. The operations ofmethod 1200 may be implemented by a UE 115 or its components asdescribed herein. According to some aspects, the operations of method1200 may be performed by a communications manager as described withreference to FIGS. 7 through 10. According to some aspects, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described below. Additionally, oralternatively, a UE may perform aspects of the functions described belowusing special-purpose hardware.

At 1205, the UE may identify that a second UE has reserved a sharedradio frequency spectrum band for sidelink communications in a channeloccupancy time, the channel occupancy time spanning a set of contiguoustime intervals. The operations of 1205 may be performed according to themethods described herein. According to some aspects, aspects of theoperations of 1205 may be performed by a shared spectrum manager asdescribed with reference to FIGS. 7 through 10.

At 1210, the UE may receive control information indicating at least oneset of interleaved frequency resources that is available for a timeinterval of the set of contiguous time intervals, the at least one setof interleaved frequency resources being one of a set of sets ofinterleaved frequency resources that frequency hop between timeintervals based on respective frequency hopping patterns. The operationsof 1210 may be performed according to the methods described herein.According to some aspects, aspects of the operations of 1210 may beperformed by a frequency hopping manager as described with reference toFIGS. 7 through 10.

At 1215, the UE may transmit, to a third UE, sidelink data in the timeinterval on the at least one set of interleaved frequency resources. Theoperations of 1215 may be performed according to the methods describedherein. According to some aspects, aspects of the operations of 1215 maybe performed by a sidelink manager as described with reference to FIGS.7 through 10.

FIG. 13 shows a flowchart illustrating a method 1300 that supportsresource configuration and reservation for sidelink communications inaccordance with aspects of the present disclosure. The operations ofmethod 1300 may be implemented by a UE 115 or its components asdescribed herein. According to some aspects, the operations of method1300 may be performed by a communications manager as described withreference to FIGS. 7 through 10. According to some aspects, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described below. Additionally, oralternatively, a UE may perform aspects of the functions described belowusing special-purpose hardware.

At 1305, the UE may identify that a second UE has reserved a sharedradio frequency spectrum band for sidelink communications in a channeloccupancy time, the channel occupancy time spanning a set of contiguoustime intervals. The operations of 1305 may be performed according to themethods described herein. According to some aspects, aspects of theoperations of 1305 may be performed by a shared spectrum manager asdescribed with reference to FIGS. 7 through 10.

At 1310, the UE may receive a feedback message transmitted by a third UEacknowledging receipt of a transmission of first sidelink data from thesecond UE. The operations of 1310 may be performed according to themethods described herein. According to some aspects, aspects of theoperations of 1310 may be performed by a feedback manager as describedwith reference to FIGS. 7 through 10.

At 1315, the UE may identify resources reserved for a retransmission ofthe first sidelink data from the second UE to the third UE. Theoperations of 1315 may be performed according to the methods describedherein. According to some aspects, aspects of the operations of 1315 maybe performed by a resource identifier as described with reference toFIGS. 7 through 10.

At 1320, the UE may initiate a listen-before-talk procedure to gainaccess to the identified resources for at least one interval of thechannel occupancy time. The operations of 1320 may be performedaccording to the methods described herein. According to some aspects,aspects of the operations of 1320 may be performed by a LBT manager asdescribed with reference to FIGS. 7 through 10.

At 1325, the UE may transmit, based on a result of thelisten-before-talk procedure, second sidelink data to a fourth UE on theidentified resources based on receiving the feedback message. Theoperations of 1325 may be performed according to the methods describedherein. According to some aspects, aspects of the operations of 1325 maybe performed by a sidelink manager as described with reference to FIGS.7 through 10.

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Aspects of the following examples may be combined with any of theprevious examples or aspects described herein.

Example 1: A method for wireless communication implemented by a firstUE, comprising: identifying a resource pool configuration indicatingresources in a shared radio frequency spectrum band available to thefirst UE for sidelink communications, the resources comprising aplurality of contiguous time intervals; identifying a frequency hoppingpattern comprising a first set of interleaved frequency resources fortransmitting sidelink data in a first time interval of the plurality ofcontiguous time intervals and a second set of interleaved frequencyresources for transmitting the sidelink data in a second time intervalof the plurality of contiguous time intervals; and transmitting, to asecond UE, the sidelink data on the first set of interleaved frequencyresources in the first time interval and the second set of interleavedfrequency resources in the second time interval based at least in parton the frequency hopping pattern.

Example 2: The method of example 1, further comprising: performing alisten-before-talk procedure to gain access to the shared radiofrequency spectrum band for a channel occupancy time to transmit thesidelink data to the second UE, the channel occupancy time spanning atleast the first time interval and the second time interval of theplurality of contiguous time intervals.

Example 3: The method of examples 1 and 2, further comprising: receivingcontrol information indicating at least one set of interleaved frequencyresources that is available for each time interval of the plurality ofcontiguous time intervals, wherein identifying the frequency hoppingpattern comprising the first set of interleaved frequency resources inthe first time interval and the second set of interleaved frequencyresources in the second time interval is based at least in part onreceiving the control information.

Example 4: The method of examples 1 through 3, further comprising:transmitting, in the first time interval, an indication of the first setof interleaved frequency resources used for transmitting the sidelinkdata in the first time interval; and transmitting, in the second timeinterval, an indication of the second set of interleaved frequencyresources used for transmitting the sidelink data in the second timeinterval.

Example 5: The method of examples 1 through 4, further comprising:transmitting, in the first time interval, an indication of the secondset of interleaved frequency resources used for transmitting thesidelink data in the second time interval.

Example 6: The method of examples 1 through 5, further comprising:transmitting, in the first time interval, the second time interval, orboth, an indication of the frequency hopping pattern used by the firstUE to transmit the sidelink data on the first set of interleavedfrequency resources in the first time interval and on the second set ofinterleaved frequency resources in the second time interval.

Example 7: The method of examples 1 through 6, further comprising:transmitting an indication of gaps in the first time interval, thesecond time interval, or both, allocated for other UEs to performlisten-before-talk procedures to gain access to the shared radiofrequency spectrum band.

Example 8: The method of examples 1 through 7, wherein: respective setsof interleaved frequency resources available to the first UE forsidelink communications in each time interval of the plurality ofcontiguous time intervals are based at least in part on a subcarrierspacing of the time interval, a sidelink identification (ID) of thefirst UE, a resource pool ID of the respective set of interleavedfrequency resources, one or more parameters associated with grouphopping of frequency resources, or a combination thereof.

Example 9: A method for wireless communication implemented by a firstUE, comprising: identifying that a second UE has reserved a shared radiofrequency spectrum band for sidelink communications in a channeloccupancy time, the channel occupancy time spanning a plurality ofcontiguous time intervals; receiving a feedback message transmitted by athird UE acknowledging receipt of a transmission of first sidelink datafrom the second UE; identifying resources reserved for a retransmissionof the first sidelink data from the second UE to the third UE;initiating a listen-before-talk procedure to gain access to theidentified resources for at least one interval of the channel occupancytime; and transmitting, based at least in part on a result of thelisten-before-talk procedure, second sidelink data to a fourth UE on theidentified resources based at least in part on receiving the feedbackmessage.

Example 10: The method of example 9, further comprising: receivingcontrol information indicating that the resources reserved for theretransmission are released upon the third UE acknowledging receipt ofthe transmission of the first sidelink data.

Example 11: The method of examples 9 and 10, wherein the controlinformation further indicates a quantity of slots after receiving thefeedback message that the first UE is to wait before transmitting thesecond sidelink data on the resources reserved for the retransmission.

Example 12: The method of examples 9 through 11, wherein the controlinformation further indicates that the first UE is eligible to transmitusing the identified resources for the at least one interval of thechannel occupancy time.

Example 13: The method of examples 9 through 12, wherein the controlinformation comprises sidelink control information or downlink controlinformation.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned herein as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell maybe associated with a lower-powered base station, as compared with amacro cell, and a small cell may operate in the same or different (e.g.,licensed, unlicensed, etc.) frequency bands as macro cells. Small cellsmay include pico cells, femto cells, and micro cells according tovarious examples. A pico cell may cover a small geographic area and mayallow unrestricted access by UEs with service subscriptions with thenetwork provider. A femto cell may also cover a small geographic area(e.g., a home) and may provide restricted access by UEs having anassociation with the femto cell (e.g., UEs in a closed subscriber group(CSG), UEs for users in the home, and the like). An eNB for a macro cellmay be referred to as a macro eNB. An eNB for a small cell may bereferred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB.An eNB may support one or multiple (e.g., two, three, four, and thelike) cells, and may also support communications using one or multiplecomponent carriers.

The wireless communications systems described herein may supportsynchronous or asynchronous operation. For synchronous operation, thebase stations may have similar frame timing, and transmissions fromdifferent base stations may be approximately aligned in time. Forasynchronous operation, the base stations may have different frametiming, and transmissions from different base stations may not bealigned in time. The techniques described herein may be used for eithersynchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. According to someaspects, data, instructions, commands, information, signals, bits,symbols, and chips that may be referenced throughout the description maybe represented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA, or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices(e.g., a combination of a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROMor other optical disk storage, magnetic disk storage or other magneticstorage devices, or any other non-transitory medium that can be used tocarry or store desired program code means in the form of instructions ordata structures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. According to some aspects, if the software is transmitted from awebsite, server, or other remote source using a coaxial cable, fiberoptic cable, twisted pair, digital subscriber line (DSL), or wirelesstechnologies such as infrared, radio, and microwave, then the coaxialcable, fiber optic cable, twisted pair, DSL, or wireless technologiessuch as infrared, radio, and microwave are included in the definition ofmedium. Disk and disc, as used herein, include CD, laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above are also includedwithin the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication implementedby a first user equipment (UE), comprising: identifying a resource poolconfiguration indicating resources in a shared radio frequency spectrumband available to the first UE for sidelink communications, theresources comprising a plurality of contiguous time intervals;identifying a frequency hopping pattern comprising a first set ofinterleaved frequency resources for transmitting sidelink data in afirst time interval of the plurality of contiguous time intervals and asecond set of interleaved frequency resources for transmitting thesidelink data in a second time interval of the plurality of contiguoustime intervals; and transmitting, to a second UE, the sidelink data onthe first set of interleaved frequency resources in the first timeinterval and the second set of interleaved frequency resources in thesecond time interval based at least in part on the frequency hoppingpattern.
 2. The method of claim 1, further comprising: performing alisten-before-talk procedure to gain access to the shared radiofrequency spectrum band for a channel occupancy time to transmit thesidelink data to the second UE, the channel occupancy time spanning atleast the first time interval and the second time interval of theplurality of contiguous time intervals.
 3. The method of claim 1,further comprising: receiving control information indicating at leastone set of interleaved frequency resources that is available for eachtime interval of the plurality of contiguous time intervals, whereinidentifying the frequency hopping pattern comprising the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval is based at least in part on receiving the control information.4. The method of claim 1, further comprising: transmitting, in the firsttime interval, an indication of the first set of interleaved frequencyresources used for transmitting the sidelink data in the first timeinterval; and transmitting, in the second time interval, an indicationof the second set of interleaved frequency resources used fortransmitting the sidelink data in the second time interval.
 5. Themethod of claim 1, further comprising: transmitting, in the first timeinterval, an indication of the second set of interleaved frequencyresources used for transmitting the sidelink data in the second timeinterval.
 6. The method of claim 1, further comprising: transmitting, inthe first time interval, the second time interval, or both, anindication of the frequency hopping pattern used by the first UE totransmit the sidelink data on the first set of interleaved frequencyresources in the first time interval and on the second set ofinterleaved frequency resources in the second time interval.
 7. Themethod of claim 1, further comprising: transmitting an indication ofgaps in the first time interval, the second time interval, or both,allocated for other UEs to perform listen-before-talk procedures to gainaccess to the shared radio frequency spectrum band.
 8. The method ofclaim 1, wherein: respective sets of interleaved frequency resourcesavailable to the first UE for sidelink communications in each timeinterval of the plurality of contiguous time intervals are based atleast in part on a subcarrier spacing of the time interval, a sidelinkidentification (ID) of the first UE, a resource pool ID of therespective set of interleaved frequency resources, one or moreparameters associated with group hopping of frequency resources, or acombination thereof.
 9. A method for wireless communication implementedby a first user equipment (UE), comprising: identifying that a second UEhas reserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a plurality of contiguous time intervals; receiving a feedbackmessage transmitted by a third UE acknowledging receipt of atransmission of first sidelink data from the second UE; identifyingresources reserved for a retransmission of the first sidelink data fromthe second UE to the third UE; initiating a listen-before-talk procedureto gain access to the identified resources for at least one interval ofthe channel occupancy time; and transmitting, based at least in part ona result of the listen-before-talk procedure, second sidelink data to afourth UE on the identified resources based at least in part onreceiving the feedback message.
 10. The method of claim 9, furthercomprising: receiving control information indicating that the resourcesreserved for the retransmission are released upon the third UEacknowledging receipt of the transmission of the first sidelink data.11. The method of claim 10, wherein the control information furtherindicates a quantity of slots after receiving the feedback message thatthe first UE is to wait before transmitting the second sidelink data onthe resources reserved for the retransmission.
 12. The method of claim10, wherein the control information further indicates that the first UEis eligible to transmit using the identified resources for the at leastone interval of the channel occupancy time.
 13. The method of claim 10,wherein the control information comprises sidelink control informationor downlink control information.
 14. An apparatus for wirelesscommunication at a first user equipment (UE), comprising: a processor,memory coupled with the processor; and instructions stored in the memoryand executable by the processor to cause the apparatus to: receive aresource pool configuration indicating resources in a shared radiofrequency spectrum band available to the first UE for sidelinkcommunications, the resources comprising a plurality of contiguous timeintervals; identify a frequency hopping pattern comprising a first setof interleaved frequency resources for transmitting sidelink data in afirst time interval of the plurality of contiguous time intervals and asecond set of interleaved frequency resources for transmitting thesidelink data in a second time interval of the plurality of contiguoustime intervals; and transmit, to a second UE, the sidelink data on thefirst set of interleaved frequency resources in the first time intervaland the second set of interleaved frequency resources in the second timeinterval based at least in part on the frequency hopping pattern. 15.The apparatus of claim 14, wherein the instructions are furtherexecutable by the processor to cause the apparatus to: perform alisten-before-talk procedure to gain access to the shared radiofrequency spectrum band for a channel occupancy time to transmit thesidelink data to the second UE, the channel occupancy time spanning atleast the first time interval and the second time interval of theplurality of contiguous time intervals.
 16. The apparatus of claim 14,wherein the instructions are further executable by the processor tocause the apparatus to: receive control information indicating at leastone set of interleaved frequency resources that is available for eachtime interval of the plurality of contiguous time intervals, whereinidentifying the frequency hopping pattern comprising the first set ofinterleaved frequency resources in the first time interval and thesecond set of interleaved frequency resources in the second timeinterval is based at least in part on receiving the control information.17. The apparatus of claim 14, wherein the instructions are furtherexecutable by the processor to cause the apparatus to: transmit, in thefirst time interval, an indication of the first set of interleavedfrequency resources used for transmitting the sidelink data in the firsttime interval; and transmit, in the second time interval, an indicationof the second set of interleaved frequency resources used fortransmitting the sidelink data in the second time interval.
 18. Theapparatus of claim 14, wherein the instructions are further executableby the processor to cause the apparatus to: transmit, in the first timeinterval, an indication of the second set of interleaved frequencyresources used for transmitting the sidelink data in the second timeinterval.
 19. The apparatus of claim 14, wherein the instructions arefurther executable by the processor to cause the apparatus to: transmit,in the first time interval, the second time interval, or both, anindication of the frequency hopping pattern used by the first UE totransmit the sidelink data on the first set of interleaved frequencyresources in the first time interval and on the second set ofinterleaved frequency resources in the second time interval.
 20. Theapparatus of claim 14, wherein the instructions are further executableby the processor to cause the apparatus to: transmit an indication ofgaps in the first time interval, the second time interval, or both,allocated for other UEs to perform listen-before-talk procedures to gainaccess to the shared radio frequency spectrum band.
 21. The apparatus ofclaim 14, wherein respective sets of interleaved frequency resourcesavailable to the first UE for sidelink communications in each timeinterval of the plurality of contiguous time intervals are based atleast in part on a subcarrier spacing of the time interval, a sidelinkidentification (ID) of the first UE, a resource pool ID of therespective set of interleaved frequency resources, one or moreparameters associated with group hopping of frequency resources, or acombination thereof.
 22. An apparatus for wireless communication at afirst user equipment (UE), comprising: a processor, memory coupled withthe processor; and instructions stored in the memory and executable bythe processor to cause the apparatus to: identify that a second UE hasreserved a shared radio frequency spectrum band for sidelinkcommunications in a channel occupancy time, the channel occupancy timespanning a plurality of contiguous time intervals; receive a feedbackmessage transmitted by a third UE acknowledging receipt of atransmission of first sidelink data from the second UE; identifyresources reserved for a retransmission of the first sidelink data fromthe second UE to the third UE; initiate a listen-before-talk procedureto gain access to the identified resources for at least one interval ofthe channel occupancy time; and transmit, based at least in part on aresult of the listen-before-talk procedure, second sidelink data to afourth UE on the identified resources based at least in part onreceiving the feedback message.
 23. The apparatus of claim 22, whereinthe instructions are further executable by the processor to cause theapparatus to: receive control information indicating that the resourcesreserved for the retransmission are released upon the third UEacknowledging receipt of the transmission of the first sidelink data.24. The apparatus of claim 23, wherein the control information furtherindicates a quantity of slots after receiving the feedback message thatthe first UE is to wait before transmitting the second sidelink data onthe resources reserved for the retransmission.
 25. The apparatus ofclaim 23, wherein the control information further indicates that thefirst UE is eligible to transmit using the identified resources for theat least one interval of the channel occupancy time.
 26. The apparatusof claim 23, wherein the control information comprises sidelink controlinformation or downlink control information.